DESCRIPTION: (Applicant's Abstract) This study aims to analyze trends in HIV incidence, HIV prevalence, and HIV risk behaviors in a longitudinal study of street-recruited injection drug users (IDUs) spanning 12 years in San Francisco. Interventions implemented in San Francisco during that time to prevent transmission of HIV among IDUs have included HIV testing and counseling (by the applicant and others), drug treatment, community health outreach with "bleach and teach" protocols, and syringe exchange programs. In the proposed study, data collected prospectively from 1986 through 1997 will be analyzed to assess the impact of HIV prevention interventions implemented during this period, and to better understand the changing epidemiology of HIV infection in the wake of these interventions. Although funding for this study was provided initially by NIDA (grant # R01-DA04212, 1986-1989), for the past 8 years, data have been collected with funds provided by the local health department for the purpose of HIV prevention, not research. As a consequence, resources have not been provided for data analysis since 1989, and the extensive opportunities for epidemiologic and prevention research have not been fully exploited. The proposed study will therefore accomplish substantial research objectives without the need for additional data collection and with a relatively small expenditure of funds. The specific aims of this study are: 1) to determine trends in HIV incidence and factors associated with HIV seroconversion among street-recruited IDUs in San Francisco, 1986 to 1997; 2) to determine trends in HIV prevalence from 1986 to 1997 and trends in factors associated with HIV prevalence among street-recruited injection drug users, and to analyze possible reasons for the observed decline in seroprevalence from 1995 through 1997; 3) to determine trends in HIV risk behaviors and factors associated with changes in injection-related and sex-related risk behaviors among street-recruited IDUs, 1986 to 1997. Factors to be examined for their association with HIV incidence, HIV prevalence, and HIV risk behaviors will include sociodemographic characteristics, risk behaviors, and exposure to HIV prevention interventions.